> >
> > You can also use symbol-macros like CLOS does for instance variables.
;; compare how to access the instance variable in abbreviated form
;; first solution (standard) is unabbreviated
;; second solution (manually) does a manual encapsulation
;; third solution (pcl-style) defines a frontend macro
(defstruct foo
a b c)
;; aux function, ignore
(defun do-some-fancy-stuff-with (p1 p2)
(print (+ p1 p2)))
(defun standard (instance-of-foo)
(do-some-fancy-stuff-with (foo-a instance-of-foo) (foo-b instance-of-foo))
(print (+ (foo-a instance-of-foo) (foo-b instance-of-foo) 1)))
(defun manually (instance-of-foo)
(symbol-macrolet ((a (foo-a instance-of-foo))
(b (foo-b instance-of-foo)))
(do-some-fancy-stuff-with a b)
(print (+ a b 2))))
;; And now for the nice stuff.
;; With best wishes to jrm - are you on this list?
(defmacro with-struct-abbrev ((varname structname &rest members) &rest body)
(let (let-bindings)
(dolist (member members)
(push (list member
(list
(intern (format nil "~a-~a" structname member))
varname))
let-bindings))
`(let ,let-bindings
,@body)))
(defun pcl-style (instance-of-foo)
(with-struct-abbrev (instance-of-foo foo a b)
(do-some-fancy-stuff-with a b)
(print (+ a b 3))))
(defun main ()
(let ((instance-of-foo (make-foo :a 42 :b 43 :c 44)))
(standard instance-of-foo)
(manually instance-of-foo)
(pcl-style instance-of-foo)))
